Personality disorders (PDs, DSM III-R Axis II disorders) are important problems leading to significant impairment of function and requiring extensive treatment. In many cases they occur along with one or more Axis I psychiatric diagnoses as comorbid conditions. In such cases a more negative prognosis is found. Because PDs are assumed to represent relatively stable characteristics that are usually first identifiable in adolescence, the impact of comorbidity on young adult outcome is of special interest. The proposed study will test a series of hypotheses generated by four different theoretical approaches to understanding personality disorders: developmental, constitutional-temperament, interpersonal, and spectrum/genetic approaches. Tests of these hypotheses will employ data on Axis I and Axis II psychiatric diagnoses collected at three times in a ten year period on about 800 late adolescents and young adults by structured diagnostic interviews of the youths and their mothers. this unique data set on a random sample of youth includes assessment of relevant measures at 4 points in time beginning when the children were age 1 through 10. Measures of temperament, developmental role function, and interpersonal problems in these assessments will be employed to determine the extent to which they account for the occurrence and prognostic impact of Axis I - Axis II comorbidity. Family history of psychiatric disorder collected by maternal interview will add information on familial aspects of these disorders. This investigation will add to our knowledge and understanding of the processes and determinants underlying Axis I - Axis II relationships. In particular, it will provide the first systematic evidence regarding the impact of personality disorder on the persistence of Axis I diagnoses from adolescence to young adulthood in an epidemiological sample unselected for treatment.